1. Field of the Invention
The present invention relates to a wave generation circuit and a flat matrix display apparatus such as a plasma display panel (PDP) display apparatus including a drive signal generation section having such a wave generation circuit or, in particular, to a wave generation circuit including a ROM for storing data relating to a waveform and the generation thereof, sequentially reading and converting the stored data into a waveform and a flat matrix display apparatus having such a circuit.
2. Description of the Related Art
In recent years, a flat matrix display apparatus using a PDP or LCD, which can be easily reduced in thickness, has come to be used in place of a CRT. Especially, the PDP display apparatus involves a simple process, can be easily increased in size, can emit light for a high display quality, and is fast in response. Due to these reasons, the PDP display apparatus has rapidly found wide applications and has seen an increased production volume. Demand is also high for a color display in these flat matrix display apparatuses. A full-color PDP display apparatus requires a fine control of the drive waveform of a display panel drive circuit. In the PDP display apparatus, the drive waveform is normally controlled on the basis of the signal generated from a wave generation circuit. A wave generation circuit, in which the data representing a signal associated with a waveform and the control thereof are stored in a ROM for each basic period of wave generation, is widely used and the data thus stored in the ROM are sequentially read out to generate a waveform. In the case where a required data amount cannot be obtained from each reading session, the data stored for the basic period is divided into a plurality of portions, so that the data are read a plurality of times for each basic period to output the required amount of data. The present applicant has disclosed a drive wave generation circuit for the PDP display apparatus having such a configuration in JP-A-4-284491.
The drive wave generation circuit for the PDP display apparatus includes a ROM for storing a drive waveform and a control signal corresponding to one subframe. If the drive waveform and the control signal corresponding to one subframe are to be stored as data in its entirety, a ROM of a large capacity would be required. For the portions where the same waveform is repeated, therefore, a predetermined address range is repeatedly read to generate the same waveform repeatedly. Also, in the case where the number of bits in the ROM is smaller than the one required to form a unit of waveform data, the ROM data is read a plurality of times to generate a unit of waveform data.
In the PDP display apparatus, in order to further improve the display quality and the durability, the drive of the panel by each driver is required to be controlled more finely. This in turn requires a finer drive waveform supplied to each driver. For the drive waveform to be finer, however, it is necessary to increase the capacity of the ROM for storing the data of the drive waveform and the control signal on the one hand and to increase the amount of the data read from the ROM within a basic period on the other hand. This indicates an increased rate at which the data is read from the ROM. An increased rate of reading the data from the ROM requires the use of a ROM of higher speed and gives rise to the problem of an increased ROM cost. For these reasons, a fine drive waveform for the PDP display apparatus has so far not been obtained easily.
The PDP display apparatus also sometimes requires that the operation is omitted for a part of a subframe and the next process is performed. In the conventional wave generation circuit, however, all that could be done was to change the addresses sequentially or to repeat a predetermined address range, but not to skip a given address to another address in reading the ROM in compliance with an external request.
All these inconveniences are not limited to the wave generation circuit used in the PDP display apparatus, but apply equally to the wave generation circuits for other applications, in which generation of a finer waveform or deformation of a waveform poses a similar problem.